1. Technical Field
Embodiments of the present invention relate to an adhesive film for polarizing plates, an adhesive composition for forming the same, a polarizing plate including the same, and an optical display device including the same.
2. Description of the Related Art
A polarizing plate includes a polarizer including an iodine compound or a dichroic polarization material arranged in a predetermined (or set) direction. The polarizing plate may include a plurality of layers, including protective films, such as triacetyl cellulose (TAC) films, on two sides of the polarizer to protect the polarizer. Further, in order to create a good visual effect, the polarizing plate may further include a wide viewing angle compensation film, such as a retardation film or a liquid crystal film having a unidirectional molecular arrangement.
Recently, the market for slimmer (or thinner) liquid crystal display devices, such as a slim (or thin) large wall-hanging television (e.g., a TV having a large display area), mobile computers (e.g., laptop computers), displays for automobiles, cellular phones, and the like has dramatically expanded. Accordingly, thin layered and lightweight thin film type polarizing plates are useful.
Including an active energy ray curable compound into an adhesive film requires additional investment costs. Additionally, irradiation of the active energy ray curable compound with an active energy ray after bonding the adhesive film with a retardation film produces transient heat, which makes it difficult to achieve desired optical properties by changing the optical properties of the retardation film. Because an adhesion imparting agent or a plasticizer included in the adhesive film is generally composed of low molecular weight polymers, there can be severe deterioration in the physical properties of the adhesive film due to surface migration of the adhesion imparting agent or plasticizer when the adhesive film is irradiated with the active energy ray for a long period of time. Further, the addition of low molecular weight polymers can reduce the cohesiveness and storage modulus of an adhesive layer (or film), thereby deteriorating the durability of the adhesive film. For example, when a retardation film having low air permeability is used, it is difficult to inhibit bubbling at high temperatures. In addition, an adhesive film including a copolymer including 5 wt % or less of an amino group-containing acrylate can exhibit low durability when the adhesive film has a thickness of 5 μm or less.